Exhaust gas recirculation is a practice that has been used to reduce emissions since the 1970s. The exhaust gas recirculation system, or EGR, routes some of the exhaust gases back into the intake manifold so they can enter the combustion chamber a second time.
Although it may sound strange, this emission reduction practice actually has a number of tangible benefits for your engine. The reduction in charge air volume (the “unburnt” air) means the throttle plate can open wider, which increases engine efficiency by reducing pumping losses.
This leads to improved fuel economy. Newer EGR systems can even reduce temperatures in the combustion chamber by cooling the exhaust gases.
What is an EGR Valve?
The EGR valve is also known as the exhaust gas recirculation valve. The purpose of this valve is to help recirculate the engine’s emissions by returning them to the combustion chamber instead of releasing them into the exhaust and out the tailpipe.
All the exhaust gases of a vehicle are dependent on the EGR valve to manage their flow. The EGR valve works in conjunction with the EGR system in order to pull this off. When the EGR valve opens, it allows emissions to enter the EGR system which is where the emissions are controlled.
Exhaust gases are typically only recirculated in low or medium load cruising scenarios. This means the EGR valve will stay closed at idle and at full throttle, preventing these exhaust gases from entering the combustion chamber.
If there is a problem with the EGR valve, then it may not be able to open and close properly. This could increase emissions and reduce fuel economy, which is the opposite of what the EGR system is supposed to do. You may not necessarily realize this is happening until you notice some of the more obvious symptoms.
Read also: 5 Symptoms of a Low Engine Oil in Your Car
Top Bad EGR Valve Symptoms
Here are some of the most common signs that you have a faulty EGR valve.
1) Check Engine Warning Light
The Check Engine light will likely illuminate on the dashboard when you have a failing or bad EGR valve. This happens as soon as the vehicle’s central computer detects that the EGR valve is in an abnormal position.
For example, if the EGR valve does not close all the way or open all the way when it is supposed to, then the computer will detect something is wrong and activate the Check Engine Light.
2) Poor Engine Performance
Although the EGR system is supposed to reduce cylinder temperatures, you wouldn’t want the EGR valve stuck open all the time. If the valve is open under full throttle, there will be less combustible air in the engine when you need it most.
A bad EGR valve is going to cause performance problems with the engine. You will likely experience acceleration difficulties and an overall power reduction when you step on the gas pedal. This is due to the air and fuel ratio being out of whack.
As a result, the engine will require more fuel just to have any power at all. Then you will be spending more money on gas because you will have a bad fuel economy as well as bad fuel efficiency.
3) Fuel Smell
Since the engine will be consuming more fuel, more hydrocarbons are going to exit the tailpipe. This will intensify the fuel odor to the point where passengers can smell it inside the cabin of the vehicle.
You obviously won’t want to keep on smelling this because it is not healthy. So, this will be an incentive to address the EGR valve problem right away.
4) Rough Idle
The engine will likely experience rough idling when there is a malfunctioning EGR valve that gets stuck in an open position. The EGR system is not designed to recirculate at idle as it may cause unstable combution that is very noticeable when you expect a smooth idle.
5) Failed Emissions Test
If you live in a state that requires you to get emissions testing every couple years, you may discover that you have a bad EGR valve if you end up failing this test. You won’t necessarily be told this, but it will be something to watch out for if you do fail.
6) Engine Knock
Most EGR systems are cooled. If the EGR system loses its coolant, the engine may experience knock or predetonation. Knock tends to happen if the intake air temperatures are too high, the air fuel ratio is off, the timing is too aggressive for the ambient conditions, or there is too much carbon buildup in the intake system.
7) Surging or Stalling
An EGR valve that is clogged or stuck open when the ECU expects the valve to be closed could throw off the air fuel ratio. This may cause a surging or stalling condition under acceleration. This may also trigger your vehicle’s limp mode or fail-safe mode.
EGR Valve Replacement Cost
The cost to replace an EGR valve can be anywhere from $300 to $800. The parts costs alone will be somewhere between $150 and $400. The labor costs will be between $150 and $400, depending on the mechanic’s hourly rate.
While an EGR valve isn’t the cheapest component to replace, especially on some vehicles, the good news is that it should not take more than one hour for the mechanic to perform this replacement job.